Currently, there are several ways to cement a production casing. One way is to employ a wiper plug system that includes a top wiper plug having a closed top end and drop the system into the casing. This method, however, leaves a closed system within the casing requiring a tubing conveyed perforation gun to blow through the casing and the cement between the casing and the hydrocarbon reservoir or formation in order for future injection or fracking fluid to access the formation.
Another way is to employ a wiper plug system, install a toe sleeve or toe valve on the downhole end of the casing, and drop the system into casing allowing the system to pass through the toe sleeve and the toe sleeve to slide behind the system. This method leaves a closed system allowing pressure to be applied against the closed top of the top wiper plug to achieve a casing pressure test. Another pressure is then applied over that of the casing pressure test to open the toe sleeve. An open toe sleeve allows injection or fracking fluid to access the formation. Although this method eliminates the use of a tubing conveyed perforation gun, it still requires installing toe sleeve toward the end of the casing and a subsequent pressure application to access the formation.
The different methods that have been employed while somewhat useful still have shortcomings such that there remains a need for further improvements in casing wiper plug systems. These are now provided by the present invention.